In document scanners, and other media transport systems, hardcopy media may sometimes jam as the hardcopy media moves along the media transport path. Objects like staples and paper clips are commonly used to hold hardcopy media containing several sheets together. Before transporting these hardcopy media through the media transport path of document scanners and other imaging devices, the operator typically removes these staples and paper clips. However, sometimes the operator fails to remove these staples and paper clips, or fails to notice them on the media, before the media are transported through the document scanner. These staples and paper clips often cause damage to the hardcopy media, the transport media path, or the document scanners itself. In addition, if two or more hardcopy media attached by a staple or paperclip are transported through the media transport path then information can be lost due to hardcopy media not be imaged properly.
While others have implemented systems to check for staples before documents go from an input tray into a scanner device, these systems are limited in the scope of detection and may miss staples, paper clips, or other objects included in media transported into the system, and thus jams may still occur. In addition, these systems do not provide a way to locate the position of a jam within the media transport system. For example, U.S. Pat. No. 5,087,027 includes a document handler system with a staple detector to detect the presence of staples in documents loaded into an input tray. However, this system only looks for staples in predetermined areas of the document, and only looks for staples while the documents are in the input tray. Some documents do not fit into the input tray, and thus no staples in these documents would be detected before they are passed into the scanner. Additionally, many types of documents, including those of varying sizes, do not have a “preselected” area for a staple. Thus, this system may miss staples in documents where staples are present, but are not in a preselected position on the document that the staple detector is monitoring.
There remains a need for a simple, fast and robust technique to monitor hardcopy media input to a media transport system for staples, paper clips, or other metal objects, and to indicate the location of hardcopy media jams along a hardcopy media transport path should a jam occur.